Throughout the world's history, conquerors have amassed land and built empires. Their influences often live on long past the death of the conqueror and sometimes transform the course of history.

Over the history of the world, lands have changed hands many times. Often, the world's most significant changes result when a powerful leader emerges, assembles an army, takes over the land around them through the use of or the threat of mass violence, and begins to amass an empire. This leader's descendants may continue to amass territory, or alternatively, they may prove incapable of controlling the newly conquered people and may succumb to the forces of a new empire builder.

The impact of a conqueror may continue long after the empire's decline, however. A few examples from ancient history illustrate the profound effects conquerors from different times and places have had on the culture of the people they conquered and on the subsequent history of the world.

Alexander

Born in 356 B.C.E. to King Philip II of Macedonia, Alexander, who would come to be known as Alexander the Great, became king upon his father's death in 336 B.C.E.—he was just 20 years old. Alexander quickly set about expanding his kingdom, applying both his military acumen and diplomatic skills. By the time he died at the age of 32, Alexander had amassed a huge empire that extended from Macedonia to Egypt and from Greece to part of India—the largest empire in the ancient world.

Alexander was keen to learn everything he could. He enlisted scientists to travel with the army in order to record information about the flora, fauna, and geography of his new territories. Alexander encouraged his people to live among and marry the people they conquered as part of his goal toward a unified empire. He also founded cities (often named Alexandria) as centers of Greek government and learning; the most famous was Alexandria, Egypt, which would continue as a center of learning long after his death. Indeed, Alexandria today is a thriving cosmopolitan city, which is home to over five million people and is an essential economic hub in modern-day Egypt.

Alexander's conquests spread Greek culture, language, and ideas throughout Asia Minor (composed mostly of modern-day Turkey), Egypt, and India. Greek culture became entwined with local cultures, bringing about changes so significant historians have a dedicated name for it: the Hellenistic Age or Period. The Hellenistic Period began after the death of Alexander the Great in 363 B.C.E. Hellenistic culture flourished and evolved in the kingdoms that followed Alexander's death. The kings of the Hellenistic lands showed off their wealth through elaborate palaces and commissioned art, sculptures, and jewelry. The Hellenistic kingdoms also encouraged learning by creating and sponsoring libraries, including the famous library at Alexandria, Egypt. Aristotle, Euclid, Archimedes, and other scientists and philosophers contributed to academic advances in this period. Koine, a form of Greek, became a common language, further facilitating the spread of ideas and Greek culture. This period came to an end when Roman troops captured the last of the territories of Alexander's empire at the Battle of Actium in 31 B.C.E.

The Norman Conquest

About a thousand years after Alexander's conquests, England would undergo as dramatic a cultural change as did Alexander's conquered territories. In 1066, King Edward of England died without an heir, and his brother-in-law Harold assumed the throne. Believing he had a better claim to the title of king than Harold, William, the duke of Normandy, gathered an army and launched an attack on England. Harold was killed at the Battle of Hastings, and William was crowned the new king, bringing an end to 600 years of Anglo-Saxon rule. Today, this event is remembered as the Norman Conquest.

The Norman Conquest had a dramatic impact on the political and social landscape of England. After assuming the throne, William ordered a comprehensive survey of the land and its resources. The results were recorded in the Domesday Book, and enabled William to tax his subjects more effectively. He also introduced the Norman system of feudalism to England, as he took land from the English elite to give to Norman nobles who pledged their allegiance to him. Together, these changes turned England into a powerful and well-organized feudal state. William also formed the Great Council, a group of nobles and church leaders, establishing a precedent for enlisting nobles in making decisions. The Great Council would eventually evolve into what is now known as the British Parliament.

The Norman Conquest also influenced culture and architecture. Castles were introduced to England, built to protect against both foreign invasion and domestic insurrection. The Normans also built churches and soaring cathedrals more typical of continental Europe. The language changed, too, as French became the language most commonly used in legal and administrative circles. Still today, the motto on the British Coat of Arms is not in English but French: "Dieu et mon droit" (God and my right).

The Mongol Empire

A few hundred years after the Norman Conquest, the Mongol Empire emerged in Asia. At its peak in the 14th century, the Mongol Empire stretched from China to Eastern Europe, making it the largest contiguous empire in world history. Perhaps it is no surprise that these conquerors would change the history of the world.

Some of the impacts of the Mongols' conquests were felt for hundreds of years. They destroyed irrigation systems in present-day Iraq and Iran, ruining the area's agricultural system and contributing to instability of the region. But, ironically, given the reputation of the Mongols for being brutal, unforgiving enemies, the most lasting impact of the Mongol Empire was the peace and stability that resulted from Mongol rule. During its heyday in the 13th century, most of the roads along the Silk Road—a network of trade routes that largely extended across Asia and into Europe—were under Mongol control. Knowledge moved freely between the Far East, the Middle East, and Europe, contributing to advances in mathematics, medicine, and astronomy. Chinese inventions and ideas spread to Europe, and European goods and ideas flowed to the Far East. Unfortunately, with these exchanges came the spread of diseases, which also traveled along the Silk Road. Research suggests the Mongols carried the plague, known in history as the Black Death, migrated from Asia to Europe, where it killed upwards of 25 million people.